Infrared optical properties of the spin-1/2 quantum magnet TiOClTiOCl

We report results on the electrodynamic response of $TiOCl$, a low-dimensional spin-1/2 quantum magnet that shows a spin gap formation for T$<T_{c1}$= 67 $K$. The Fano-like shape of a few selected infrared active phonons suggests an interaction between lattice vibrations and a continuum of low frequency (spin) excitations. The temperature dependence of the phonon mode parameters extends over a broad temperature range well above $T_{c1}$, indicating the presence of an extended fluctuation regime. In the temperature interval between 200 $K$ and $T_{c1}$ there is a progressive dimensionality crossover (from two to one), as well as a spectral weight shift from low towards high frequencies. This allows us to identify a characteristic energy scale of about 430 $K$, ascribed to a pseudo spin-gap

Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR

We present electron spin resonance data of Ti$^{3+}$ (3$d^1$) ions in single crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is predominantly occupied and owing to the occurrence of orbital order a linear spin chain forms along the crystallographic b axis. This result corroborates recent theoretical LDA+U calculations of the band structure. The temperature dependence of the parameters of the resonance signal suggests a strong coupling between spin and lattice degrees of freedom and gives evidence for a transition to a nonmagnetic ground state at 67 K.Comment: revised version, accepted for publication in Phys. Rev. B, Rapid Com

An investigation into the 3d1 and 3d2 transition Metal halides and oxyhalides considered as being close to delocalisation

SIGLEAvailable from British Library Document Supply Centre- DSC:DX81216 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Second-order kinetic analysis of IAsys biosensor data: Its use and applicability

The kinetic analysis of IAsys biosensor association data usually relies upon the assumption of constant ligate concentration. In certain circumstances this assumption may no longer be valid. In a similar vein, the analysis of the dissociation phase assumes the concentration of ligate to be negligible in the liquid phase - an assumption that may not be sustainable for high-affinity interactions. In this paper we derive analytical solutions of the second-order differential kinetic equations for the association and dissociation phases, together with a binding isotherm that also allows for changes in concentration of both the ligand and the ligate. Using these equations it is possible to determine the conditions under which the pseudo- first-order assumption ceases to be valid. It is found that the effect of ligate depletion on the association rate constant becomes significant only when binding low ligate concentrations to ligand on surfaces with high binding capacities or high affinities. Similarly, the rebinding in the dissociation phase is dependent upon the affinity and the ligand capacity together with the starting dissociation response compared to the capacity. Finally, depletion also affects the form of the binding isotherm, particularly in situations involving high matrix capacities for ligate and high-affinity interactions